452 
THE GEOLOGIST. 
would acquire a crystalline nat,ure. Tims some of tlic ingredients fomid as 
couipoueuts of granite and other igneous roeivs would be dcvelo))cd. This 
may be supj)osed to be the effect of lieat, which would affect what woidd 
otherwise be ordinarily stratiiled rocks. I consider tliat tliis hypothesis is 
nnicli strengtlicued by tlic fact (assuming, as from the nature of granite I think 
I may, that this geological doctrine is a fact) that these rocks underlie those 
pro|)crly stratified and fossUiferous. The metamorphic rocks appear to be 
ordinary stratified rocks subjected to the influence of heat. The hypothesis 
alluded to, if accepted as true, or even probable, explains their position. The 
heat of the igneous rocks would not reach those purely sedimentary, but only 
alter rocks with which they were directly connected. If it be said, as it has 
been, that some metamorplue rocks do not exhibit the influence of heat, I ad- 
vise that the objectors consider the effect of age upon any deposit ; and also 
the way, the possible way, in which this phenomenon can be aeeounted for, if 
they can discover any, and reject this explanation. I do not see what other 
explanatory hy^jotliesis can be found. — I. A. Davies. — How sedimentary mat- 
ter or any precipitate eoidd be derived from higldy heated basement-rock, as 
Lardner's hypothesis requires, it is difficult to conceive. As altered sedi- 
mentary matter (sand, clay, and limestone) the materials of the metamorphic 
rocks might plainly have come from the waste of the first uprising lands. 
The position of the metamorpliic rocks in relation both with the igneous rocks 
and unaltered sedimentary rocks affords incontrovertible evidence of their 
having been usual sediments altered and distorted by heat. 
Suggestion respecting Rock-basins. — Sir, — Whilst reading in your 
periodical for August the interesting article by Mr. Kupert Jones on the 
weathering of granite, a conjecture presented itself to me as to the pro- 
bable cause of tlic primary basins on some of the surfaces of the granite. It is 
this — whether the basins, if they correspond with distinct masses of rock, may 
not be produced by the shrinking of compressed cooling masses. I might add 
in illustration, I conceived that a like process might occasion the concave and 
convex jomts in the basaltic pillars at the Giant's Causeway. This is merely 
a suggestion, which may or may not be tenable ; if it be, you are quite at 
liberty to publish it should you think fit.- — Yours respectfully, George Renning, 
Sheffield. — Our correspondent v/iii see in Mr. Rupert Jones' paper, at pages 
307 and 308, that the effects of contraction in cooling have not escaped observa- 
tion ; and lie will further see, at page 311, that Mr. Ormerod recognizes the 
horizontal planes of fracture or fissurage as probably limiting the depth of at 
least some of the basins. We may take this occasion, in reference to the re- 
marks of our correspondent, Mr. Drake, ia our September number, on the artificial 
origiu of rock-basins, to express our regret that Mr. Rupert Jones did not refer 
to that interesting aspect of the subject ; probably he wished that readers 
should refer on this point to Mr. Omerod's valuable memoir from which he 
largely quoted, and in which wiU be found some observations on the circular 
cavities m boulder-blocks in stream-courses, to which class of basins Mr. Drake 
refers in the latter part of his communication. 
Localities for Mammalian Remains. — Bones of elephant, rhinoceros, 
and ox from the gravel, at BrockliaU, Lawford, were presented to the Geological 
Society, in 1833, by the Rev. Wm. Thornton. Shells, and bones of inainmalia, 
from Stutton, Suffolk, were also presented by Mr. Edw. Chaiiesworth in 1835. 
— 1\G.S., London. 
